1. Field of the Invention
The present invention relates to a cardiotachometer with visual readout and, more particularly, to a cardiotachometer that is worn by a user for determining the pulse rate based upon the time between two consecutive heartbeats after a predetermined delay and for immediately displaying the determined pulse rate numerically.
2. Description of the Prior Art
Heart rate is a basic parameter used to evaluate and determine the condition of the human body. It is for this reason that every patient in every hospital has his or her pulse taken at least once a day. The pulse rate is customarily determined by a nurse placing her fingers against the volar aspect of the wrist or the carotid artery of the neck and counting the number of beats per minute.
These beats per minute refer to the number of systoles per minute. A systolic heartbeat is that period in the functioning of the heart when it is contracting and forcing blood through the arteries in the course of which the arteries expand. This arterial expansion is that which is sensed through the nurse's fingers or by an appropriate transducer situated against the carotid artery or volar aspect, or any other well-known pressure point.
In the case of a transducer being applied to a pressure point, electrical impulses are produced which may be supplied to appropriate electronic circuitry for determining the systolic pulse rate. In the past, the electronic pulse rate measurement devices have required a relatively long time period to determine the pulse rate.
More recently, electronic pulse rate measurement devices have determined the pulse rate by measuring the time between two consecutive heartbeats. An undesirable feature of this procedure is that movements of the user are not distinguished from the systolic pulse by the transducer and thus false readings occur. To avoid such false readings, electronic pulse rate measuring devices have been designed to average the time intervals over ten or fifteen systolic heartbeats. The averaging technique results in a more accurate indication of pulse rate, but involves too much time for the measurement and error is averaged as well as the desired signals.
The present cardiotachometer utilizes miniaturized, solid state circuits, including a piezoelectric crystal as the pressure transducer to be placed against the volar aspect or the temple of the user. To eliminate the noise signals generated from movement by the patient, a present delay is incorporated during which time the patient must remain quiet to avoid noise input. Then an accurate reading is taken by measuring the time between two consecutive heartbeats.